Answer the following questions:
- Write the scientific name of the fruit fly.
- Why did Morgan prefer to work with fruit flies for his experiments? State two reasons.
- Write the scientific name of the fruit fly.
- Why did Morgan prefer to work with fruit flies for his experiments? State two reasons.
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Solution and Explanation
- The scientific name of the fruit fly is Drosophila melanogaster.
- Morgan preferred fruit flies for the following reasons:
- They have a short life cycle and reproduce quickly.
- They produce a large number of offspring and show clear genetic variations.
Top Questions on Principles of Inheritance and Variation
In a certain population, the frequency of three genotypes is as follows:
Genotypes: PP Pp pp
Frequency: 22% 62% 16%
Choose the option that shows the frequency of P and p alleles correctly:- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
- Assertion (A): A male individual always inherits haemophilia from his mother.
Reason (R): The gene for haemophilia lies on X-chromosome.- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
- Which of the following conditions correctly describes the manner of determining the sex in the given options?
- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
Answer the following questions:
(a)
- What is a test cross? How can we find out the zygosity of a plant by the use of test cross?
- Why are human females rarely haemophilic? Explain with the help of a cross. Under what conditions can a haemophilic female be born? How do haemophilic patients suffer?
OR
(b) Name the two events ‘a’ and ‘c’ shown in the diagram below.
- Mention where in the cell these events take place.
- Explain the changes taking place during event ‘b’ and mention why these are needed.
- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
- Assertion (A): Human male is referred to as heterogametic.
Reason (R): The male produces millions of sperms of the same kind.- CBSE CLASS XII - 2025
- Biology
- Principles of Inheritance and Variation
Questions Asked in CBSE CLASS XII exam
Galvanometer:
A galvanometer is an instrument used to show the direction and strength of the current passing through it. In a galvanometer, a coil placed in a magnetic field experiences a torque and hence gets deflected when a current passes through it.
The name "galvanometer" is derived from the surname of Italian scientist Luigi Galvani, who in 1791 discovered that electric current makes a dead frog’s leg jerk.
A spring attached to the coil provides a counter torque. In equilibrium, the deflecting torque is balanced by the restoring torque of the spring, and we have the relation:
\[ NBAI = k\phi \]
Where:
- \( N \) is the total number of turns in the coil
- \( A \) is the area of cross-section of each turn
- \( B \) is the radial magnetic field
- \( k \) is the torsional constant of the spring
- \( \phi \) is the angular deflection of the coil
As the current \( I_g \) that produces full-scale deflection in the galvanometer is very small, the galvanometer alone cannot be used to measure current in electric circuits.
To convert a galvanometer into an ammeter (to measure larger currents), a small resistance called a shunt is connected in parallel to the galvanometer.
To convert it into a voltmeter (to measure potential difference), a high resistance is connected in series with the galvanometer.
- CBSE CLASS XII - 2025
- The Moving Coil Galvanometer
Einstein's Explanation of the Photoelectric Effect:
Einstein explained the photoelectric effect on the basis of Planck’s quantum theory, where light travels in the form of small bundles of energy called photons.
The energy of each photon is hν, where:- ν is the frequency of the incident light
- h is Planck’s constant
The number of photons in a beam of light determines the intensity of the incident light.When a photon strikes a metal surface, it transfers its total energy hν to a free electron in the metal.A part of this energy is used to eject the electron from the metal, and this required energy is called the work function.The remaining energy is carried by the ejected electron as its kinetic energy.
- CBSE CLASS XII - 2025
- Photoelectric Effect
- Two point charges \( q_1 = 16 \, \mu C \) and \( q_2 = 1 \, \mu C \) are placed at points \( \vec{r}_1 = (3 \, \text{m}) \hat{i}\) and \( \vec{r}_2 = (4 \, \text{m}) \hat{j} \). Find the net electric field \( \vec{E} \) at point \( \vec{r} = (3 \, \text{m}) \hat{i} + (4 \, \text{m}) \hat{j} \).
- CBSE CLASS XII - 2025
- Electric Fields and Gauss' Law
- A current of 5 A is passing along +X direction through a wire lying along X-axis. Find the magnetic field \( \vec{B} \) at a point \( \vec{r} = (3 \hat{i} + 4 \hat{j}) \, \text{m} \) due to 1 cm element of the wire, centered at the origin.
- CBSE CLASS XII - 2025
- Motion in Combined Electric and Magnetic Fields
- In which case is the potential energy of the magnet minimum?
- CBSE CLASS XII - 2025
- Magnetism and matter